1. Field of the Invention
The present invention relates to the preparation of methacrylic esters, and, more especially, to the preparation of such methacrylates by transesterification.
2. Description of the Prior Art
French Pat. No. 2,405,237 describes a process for the preparation of methacrylic esters by transesterification; it is stated therein that the process has been carried out in the presence of a transesterification catalyst, which consists of lithium hydroxide used in a proportion of 0.01 to 2% by weight with respect to the total weight of the reagents, as well as in the presence of a known methacrylate polymerization inhibitor. This '237 patent also notes that the reaction mixture is heated, under total reflux, until that point in time whereat the head of the column the temperature of the methyl methacrylate/methanol azeotrope is attained, such azeotrope enabling the gradual elimination of the methanol present in the reaction medium.
A systematic study of the transesterification of methyl methacrylate with higher alcohols, utilizing a lithium compound (preferably the hydroxide or carbonate) as the catalyst, has shown that it is possible and industrially attractive to only use amounts of catalyst less than those specified in said French Pat. No. 2,405,237, under such conditions that, on the one hand, the catalyst is gradually introduced into the reaction medium, and, on the other, the reaction is carried out in the presence of an inert azeotrope-forming compound which produces, with the methanol present in the reaction medium, an azeotrope boiling at a temperature of less than approximately 60.degree. C. (at atmospheric pressure).